The present invention relates to a roll control system for an automotive vehicle, and more specifically relates to a vehicle roll control system of the vehicle height adjustment type.
The present invention has been described in Japanese Patent Applications Serial Nos. Showa 60-235662 (1985) and Showa 60-235663 (1985), both of them filed by an applicant the same as the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the tests of said Japanese Patent Applications and the claims and the drawings thereof; copies are appended to the present application.
Further, the present inventors wish hereby to attract the attention of the examining authorities to copending patent applications Ser. Nos. 921,251 (issued as U.S. Pat. No. 4,693,493 on Sept. 15, 1987), 921,450, 921451, and 921468, which may be considered to be material to the examination of the present patent application.
In general, in the operational conditions where a vehicle such as an automobile turns at a speed not less than a particular determinate turning speed value, the body of the vehicle experiences rolling, i.e. the vehicle body inclines in the radially outward direction, and this rolling results in deterioration of the drivability of the vehicle and discomfort for the vehicle driver and/or the vehicle passengers.
As shown in Japanese Patent Laying Open Publication Serial No. 59-120509 (1984) and in the specification of Japanese Patent Application Ser. No. 59-172416, neither of which is it intended hereby to admit as prior art to the present patent application except to the extent in any case required by applicable law, as an approach to cope with the above identified problem, it has been suggested, while the vehicle is running round a curve, to increase the hardness and the softness characteristics of the suspension means for the vehicle, e.g. the damping force of the vehicle shock absorbers or the spring rate of the vehicle suspension springs. In such an approach, however, it is only possible to reduce the roll of the vehicle body to a lower level in comparison with the case in which no damping force increase or spring rate increase is performed, and it is not always possible to effectively prevent the vehicle body from rolling. Further background to this matter can be gleaned from Japanese Utility Model Laying Open Publication Serial No. 59-35105 (1984), Japanese Patent Laying Open Publication No. 53 -26021 (1978), Japanese Patent Laying Open Publication Ser. No. 58-167210 (1983), and Japanese Utility Model Laying Open Publication Serial No. 56-147107 (1981), none of which is it intended hereby to admit a prior art to the present patent application except to the extent in any case required by applicable law.
In order to cope with the above problem, in the case where a vehicle is fitted with a vehicle height adjustment system comprising: a plurality of actuators which are provided for resiliently suspending the vehicle wheels from its body and are adapted to increase or decrease vehicle height at locations corresponding to the associated vehicle wheels as respective results of supplying or discharging working fluid to or from variable volume working fluid chambers of said actuators; a plurality of working fluid supplying and discharging means which are provided corresponding to the actuators and which serve to supply or discharge the working fluid to or from said actuators; a vehicle height detecting means for sensing vehicle height; a control means for controlling the working fluid supplying and discharging means based upon the data sensed by the vehicle height detecting means in order to adjust the vehicle height to a determinate vehicle height, (as proposed, for example, in the specification of Japanese Patent Laying Open Publication Serial No. Sho 60-85005 (1985), which was based upon an application filed by an applicant the same as one of the applicants or one of the assignees or one of the entities owed duty of assignment of the present application, and which it is not intended hereby to admit as prior art to the present patent application except to the extent in any case required by applicable law), it might be conceived of to actively achieve vehicle height adjustment during running of the vehicle around a curve, in order to thereby prevent completely the vehicle body from rolling, by controlling the working fluid supplying and discharging means based upon the difference between the actual vehicle height and a reference vehicle height.
In a vehicle equipped with such a vehicle height adjustment system as described above, however, since the duty ratios for controlling the various actuators for the vehicle wheels (such actuators are typically controlled by duty ratio control) would be set based upon the differences between the actual vehicle heights at its wheels and reference vehicle heights at said wheels, therefore roll control by vehicle height adjustment could only be initiated at a time point when the vehicle height differences caused due to rolling of the vehicle body had become significantly large, and accordingly the problem would arise that it would be logically impossible to cancel all of the rolling of the vehicle body, at least in a case when rapid steering was being performed.